On Wed, Jun 11, 2008 at 9:12 AM, Jean-Sébastien Guay < [EMAIL PROTECTED]> wrote:
> Hi Glenn, > > Thanks for the links, combined with Chris and Alan's links I might get a > better understanding of the general terminology and concepts... That's one > thing I'm lacking now, it just sounds like a bunch of acronyms and alien > words to me :-) I thought being in computer science I'd be immune to > acronymitis by now... > > Anyway the first task is to figure out whether you need to reproject your >> data at all. UTM is a flat-earth XYZ system. Do you have a terrain? What >> spatial reference system is it in? >> > > We /will/ have a terrain, but I don't have details on it. If it's also in > UTM, we could use it directly and just not reproject anything, right? Right. So you're saying we could just, for example, decide that our world origin is > at some translation from the UTM coordinates' origin, and then translate all > the data we get by that, and be done with it? Right. Or better yet, use a MatrixTransform to place your terrain at actual UTM coordinates, and theyn you don't even have to translate the incoming data. For example, from the specs document I've got, it seems the coordinates we > might get would look like > > 576120.324, 6224420.858, -102.73 > > What units would that be in? Our models are modeled in meters, and we'd > like to use meters as world-units, so for distances to look right would we > need to scale the terrain and the position data we get? UTM coordinates are in meters. X is relative to the central meridan of the UTM zone, plus the "false easting", which exists only to avoid the use of negative numbers. Y is relative to the equator. Y values in the southern hemisphere are also given a "false northing" to avoid negative #s. > Still a bit of confusion about the basic concepts. I'll go read those links > now :-) Bottom line: if you use VPB to build a terrain in UTM zone 32 (or whatever), you will need to do no coordinate conversion. > > > J-S > -- > ______________________________________________________ > Jean-Sebastien Guay [EMAIL PROTECTED] > http://www.cm-labs.com/ > http://whitestar02.webhop.org/ > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > -- Glenn Waldron : Pelican Mapping : http://pelicanmapping.com : 703-652-4791
_______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
